Process of refining fumes



(N0 Mode-1') F. L. BARTLETT.

PROCESS OF REFINING FUMES.

Patented July 16, 1889.

Wilfp V 4 UNITED STATES PATENT OFFICE.

FRANK Ii. BARTLETT, ()F PORTLAND, MAINE.

PROCESS OF REFINING FUMES.

SPECIFICATION forming part Of Letters Patent NO. 406,868, dated July 16, 1889. Application filed August 23, 1888, Serial No. 283,568. (No model.)

To (tZZ whom it may concern:

Be it known that I, FRANK L. BARTLETT, acitizen of the United States, residing at Portland, in the county of Cumberland and State of Maine, have invented certain new and useful Improvements in the Process of Refining Fumes; andIdo hereby declare the following to be a full, clear, and exact description of the invention, such will enable others skilled in the art to which it appertains to make and use the same.

My invention relates to the manufacture of paint-pigments; and theobject of the invention is to refine and whiten the fume collected in the operation of treating lead, Zinc, and antimony ores by smelting or roasting processes.

A further object of my invention is to condense or reduce the volume of such fumes.

It is well known that in these operations fume is often collected in condensers, bags, or screens, which, by reason of its dark color, is obliged to be resmelted or revolatilized in order to render it white and pure. The dark color of this fume arises from the presence of various substances, such as the rare metals cadmium, selenium,vanadium, and tellurium, and also sulphur compounds, carbonaceous matter, and acids. The base of the fume or pigment is, however, either lead, zinc,or antimony, or compounds of these metals in the form of oxides, sulphurets, and sulphates or mixtures of the above. These fumes, when formed and collected by most of the so-called dry processes, are dark colored and impure and unfit for any purpose until they have been resmelted or resnblimed, to rid them of the impurities which they contain. llitherto no other methods have been used for refining these products except the usual ones of resubliming and resmeltingin furnaces of various kinds, and these methods of refining have been expensive and tedious owingto the bulky and light nature of the substance operated upon.

obtain pigment of uniform quality by these processes of refining.

My invention is founded upon the fact that when such fume is collected comparatively free from extraneous matter, as sand, grit, ash, iron-rust, 850., and is then subjected It has also been ditficult to to a constant degree of heat out of contact with the products of combustion, and in contact with moving surfaces and in the presence of air and is then suddenly cooled by ejecting it into the open air or otherwise, the fume becomes white, dense, and soft, and it is found to be free from the volatile sulphur compounds, acids, carbonaceous matter, and such volatile metals as selenium, arsenic, &c. The fume thus treated is fitted for a pure white pigment, has great covering power, and possesses great stability as to color, while it is condensed to one-fourth to one-eighth of its original bulk.

I illustrate in the accompanying drawings apparatus which I have invented for carrying out my process.

In the drawings, Figure 1 represents a central longitudinal section through my apparatus. Fig. 2 is a section showing detail of feeding screw or worm.

A represents a furnace or kiln composed of brick or other suitable material, having a suitable hearth C at one end. A closed chamber of considerable length leads horizontally from the hearth O to the end of the furnace, where it connects with an outletfiuc F. A tube D extends longitudinally through the chamber B and passes through the end walls of the furnace. One end of the tube D is open and the otheris connected with the bottom of a hopper G. A screw or worm E extends through the whole length of the tube D. This screw E is made preferably of iron, and may be either cast or wrought. It consists of a flat bar twisted in the form of a helix and having an opening longitudinally through the center, as clearly shown in Fig. 2. Connected with the end of the screw E is a shaft and pulley ll or other means of rotating it. An outlet pipe or flue D, for carrying off the air, connects with the tube D.

I is a hood which covers the top of the furnace, and I an outlet for the same.

In carrying out my process I place the fume to be whitened and condensed in the hopper G and rotate the screw E by means of the pulley II, having previously started a fire on the hearth C. The fume is fed slowly along the tube D by the motion of the screw and is subjected during its progress to the heat of the fire, which is kept as nearly as may be at a constant temperature. I prefer that the temperature of the fume shall not rise above 1,000- Fahrenheit. As the fume is fed along, it is continually agitated and mixed by the action of the screw, and at the same time it is subjected to a current of air which is constantly drawn or forced in and which passes in and through the fume. When the advancing stream of fume reaches the end of the tube, it is allowed to fall into the open air, whereby it is suddenly cooled; or it may be cooled in any other suitable manner. It may be said that the quicker the hot fume is cooled the more perfect will be the product. The fume is so fed to the screw that it passes through in a comparatively thin stratum, whereby it is uniformly subjected to the heat of the fire and to the action of the air.

The ordinary reverberatory, mu file, hearth, and mechanical furnaces can not be used in this process since it is necessary that each atom shall be subjected to an even degree of heat and also that it shall be in constant motion, otherwise chemical changes take place which would ruin the color of the product.

Fume treated by this process is rendered dense, fine, and white, as already pointed out. The operation, when carried out by this apparatus, is purely automatic and requires no care beyond the care of the fire.

It is desirable that the fume shall be promptly discharged when it has been in contact with the heated surface for a proper length of time, otherwise it hardens and loses its fine and soft texture. It is evident that other forms of apparatus may be designed which will carry out my process equally as well as theone here shown.

I claimv The herein-described process of refining fume, which consists in passing itthrough a heated tube in the presence of air and continually stirring and scraping it from the walls of said tube during its passage, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

FRANK L. BARTLETT.

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S. W. BATES, ILBUR F. LUNT. 

